The present invention relates to a holding brake for a traction sheave elevator, as defined in the preamble of claim 1.
The function of the holding brake is to hold the elevator car immovable at a floor and to stop the car or prevent it from moving during a power failure. For this reason, the braking effect of the holding brake is based on a mechanical compressing element, such as a spring, which keeps the brake engaged when no external forces are acting upon it. As the holding brake is activated every time when the car arrives at a floor and released every time when the car leaves a floor, its operation must be as fast, accurate and noiseless as possible so that the passengers in the elevator cannot perceive it.
Therefore, the air gap between the brake shoe of the holding brake and the brake surface on the traction sheave or a possible separate brake wheel must be as small as possible. This allows fast braking, a low impact energy of the brake shoe and as noiseless a braking action as possible.
As the holding brake must also be capable of stopping a moving car e.g. in the case of a power failure, the braking force of the holding brake, i.e. the compressive force of the spring used in it, must be relatively large. Therefore, when the brake shoe is pressed against the brake surface, this generally tends to generate some kind of noise or vibration.
The object of the invention is to eliminate the drawbacks referred to above. A specific object of the invention is to disclose a new type of structure for use in a holding brake for a traction sheave elevator, designed to damp the noise and vibration generated by the operation of the holding brake.
As for the features characteristic of the invention, reference is made to the claims.
The holding brake of the invention for a traction sheave elevator comprises a brake body, a movable frame movably connected to the brake body, a brake pad attached to the movable frame, a pulling element, such as e.g. an electromagnet, mounted on the brake body to draw the movable frame toward the brake body, and a compressing element, such as a mechanical spring, between the brake body and the movable frame for moving the movable frame away from the brake body and pressing the brake pad attached to the movable frame against the brake surface. According to the invention, the movable frame comprises a surface oriented in the direction of its motion and the brake body comprises a counter surface oriented in a corresponding direction, with a gap left between these surfaces so that the surfaces are not in direct contact with each other, a damping element being fitted in the gap between said surfaces so that it is in contact with both surfaces to damp the motion of the movable frame.
The gap between the surfaces preferably has a uniform width in the direction of motion of the movable frame. Likewise, the gap preferably forms a ring around the movable frame, in which case the damping element surrounds the movable frame like a ring. However, it is also possible to use a damping element only extending over a part of the perimeter of the movable frame.